The research deals with extractants of bark. Park of
spruce (Picea shies) was extracted with different solvent
and extraction conditions. The extraction solvent always
consisted of water and added Na2SO3, SO2 or methanol.
Solvent and extraction procedures had great influence on
extract yield and the polyphenolic content of extract
(Stiasny number). With pure water the extract yield and
tannin content of the extract were low. Using different
chemicals, such as sulphite or alkali, as mentioned
above, polyphenolics with higher yield and satisfactory
reactivities with formaldehyde could be extracted.
Especially extraction with alkali considerably increased
the yield of extracts.
In gluing experiments were made three-ply birch plywood
consisting of 250 x 250 x 1,5 mm birch veneers or
nine-ply birch plywood consisting of 500 x 500 x 1,5 mm
birch veneers. No pure tannin based adhesives were used.
Extracts were always added to different phenolic resins
(so far FXTER A or EXTER B). Plywoods were glued under
very normal gluing conditions used in industry. Plywoods
were tested as prescribes in Finnish plywood standard SFS
2416. The results showed that up to 20 % of phenolic
resins can be replaced by spruce extracts so that the
plywoods fulfilled the limits of Finnish plywood standard
SFS 2415 and Finnply quality control.
|Place of Publication
|VTT Technical Research Centre of Finland
|Number of pages
|Published - 1984
|MoE publication type
|D4 Published development or research report or study
|Valtion teknillinen tutkimuskeskus. Tutkimuksia - Research Reports
- spruce wood
- pine wood